WO2000058534A1

WO2000058534A1 - N-type semiconductor diamond and its fabrication method

Info

Publication number: WO2000058534A1
Application number: PCT/JP2000/001863
Authority: WO
Inventors: Toshihiro Ando; Yoichiro Sato
Original assignee: Japan Science And Technology Corporation; National Institute For Materials Science; Yasu, Eiji; Gamo, Mika; Sakaguchi, Isao
Priority date: 1999-03-26
Filing date: 2000-03-27
Publication date: 2000-10-05
Also published as: KR100525792B1; US7063742B1; TW471006B; JP3769642B2; EP1179621A4; EP1179621A1; KR20010114226A

Abstract

A substrate (15) is polished into an inclined substrate and is exposed to a hydrogen plasma so that it is smoothed. This substrate (15) is heated under control to a surface temperature of 830 °C, and a mixed gas containing 1 % of methane, 50 ppm of hydrogen sulfide and hydrogen is introduced at a rate of 200 ml/min. into a reaction tube (7). A microwave plasma (19) is produced to grow n-type semiconductor diamond epitaxially over the substrate (15). Thus, there is fabricated a sulfur-doped n-type semiconductor diamond having a high mobility, a high quality, and a single donor level of an activation energy of 0.38 eV.

Description

-Description n-type semiconductor diamond and its manufacturing method

INDUSTRIAL APPLICABILITY The present invention can be used for small high-power devices, high-power high-frequency devices, and electronic devices such as radiation-resistant integrated circuits, which are impossible with conventional semiconductors. The present invention relates to diamond and a method for producing the same, and more particularly to an n-type semiconductor diamond in which donor atoms are effectively added to diamond and a method for producing the same. Background art

In Si-based semiconductors and gallium arsenide semiconductors currently used, the electric field strength inside the device increases due to the miniaturization and high density of the device, and heat generation during use becomes a problem. It is required to adapt to different environments.

Diamond, on the other hand, is a wide bandgap semiconductor with the highest electron and hole mobilities, a very high breakdown field, and very few electron-hole pairs at high temperatures and under radiation. Because it can adapt to harsh environments, it can be used for devices for high power, high frequency operation, and high temperature operation. In order to realize such a diamond semiconductor device, a high-quality diamond crystal thin film is required.

Until now, low-resistance p-type semiconductor diamond could be easily manufactured by doping with boron, but a number of manufacturing methods have been studied for low-resistance n-type semiconductor diamond, including methods for doping CVD diamond. However, it was actually difficult to obtain high-quality semiconductor diamond crystal thin films.

For example, it has been reported that diamond doped with nitrogen has low activation energy and becomes an insulator at room temperature (Mat. Res. Soc. Symp. Pro 162, 3-14 (1990)). Furthermore, n-type diamond crystal thin films doped with phosphorus have been reported, but their electrical resistance is too high to be suitable for practical use (Mat. Res. Soc. Symp. Pro 162, 23-34 (1990)).

An attempt to obtain an n-type diamond thin film from methane and hydrogen sulfide by microwave plasma CVD has also been reported (Japanese Patent Application Laid-Open No. 63-32516). However, as is clear from Tables 1 and 2 of the publication, the electron mobility of the n-type semiconductor diamond thin film produced by the microwave plasma CVD method was determined by the ultrahigh pressure method shown in Table 2. Compared to the electron mobility of the obtained n-type semiconductor diamond single crystal, it shows an extraordinarily large value while having the same ion concentration. That is, this n-type semiconductor diamond thin film has many defects and cannot be applied to semiconductor electronic devices.

Further, the microwave plasma C preparation of phosphorus-doped diamond by VD method information, introducing phosphine (PH ₃₎ in the reaction gas of hydrogen and hydrocarbon doped with phosphorus by decomposing phosphine in microphone port wave plasma There is known a method of decomposing phosphine at a high temperature or under irradiation of ultraviolet rays to dope phosphorus. .

However, according to this microwave plasma CVD method, diamond is doped with phosphorus in a state of being bonded to hydrogen, so that phosphorus does not serve as an electron supplier, and even if phosphorus is doped, Since the carrier mobility of n-type semiconductor diamond is low and the level is deep, n-type semiconductors of a quality applicable to semiconductor electronic devices have not been obtained.

As described above, the CVD method has been reported on various methods for producing an n-type semiconductor diamond crystal thin film, but has not obtained a quality applicable to semiconductor electronic devices.

In addition, a method of implanting phosphorous ions into diamond by accelerating it is also known. However, in this method, phosphorus having a larger mass than carbon is implanted, causing defects in the diamond, and phosphorus is converted into carbon. Since they are interstitial in the diamond lattice without bonding, it is difficult to make bonds in the diamond lattice, and high-quality n-type semiconductor diamond has not been obtained.

In addition, as a method of bonding diamonds without using plasma, graphite and red phosphorus are placed in a reaction system, and diamond is synthesized by evaporating in the system. A chemical transport reaction method of doping with phosphorus is also known.

However, due to differences in the reaction rates and evaporation rates of graphite and red phosphorus, it is difficult to control the phosphorus concentration, and high-quality n-type semiconductors cannot be obtained.

Recently, an n-type diamond semiconductor in which a pentavalent or more valent atom is added as a donor atom has been proposed (see Japanese Patent Application Laid-Open No. 10-198489). However, an n-type semiconductor diamond that can be applied to a semiconductor electronic device doped with zirconium has not yet been realized, and its manufacturing method has been an issue.

The present invention solves such problems in the conventional technology. As a first object, the present invention provides a manufacturing method capable of obtaining an n-type diamond having perfect crystallinity applicable to a semiconductor electronic device. It is to be.

A second object is to provide an n-type semiconductor diamond having perfect crystallinity applicable to semiconductor devices. Disclosure of the invention

In order to achieve the first object, a method for producing an n-type semiconductor diamond according to the present invention includes: a process of turning a diamond substrate into an inclined substrate by mechanical polishing; a process of smoothing the surface of the inclined substrate; A source gas consisting of volatile hydrocarbons, whey compounds, and hydrogen gas is excited by microwave plasma, and an n-type semiconductor diamond is epitaxially grown on a smoothed substrate while maintaining a predetermined substrate temperature. Processing steps.

As the diamond substrate, a diamond (100) plane orientation substrate is used.

In addition, the inclined substrate is a plane in which the surface normal of the diamond (100) plane is defined by the <100> direction or the <110> direction or the <100> direction. It is formed by mechanical polishing so as to be inclined at any angle in the range of 1.5 to 6 degrees with respect to the <100> direction.

The smoothing treatment is preferably a treatment in which the inclined substrate is exposed to hydrogen plasma or a treatment in which the inclined substrate is exposed to an oxidizing flame of a combustion flame such as acetylene.

By these treatments, the surface of the substrate is smoothed in the atomic order, and a surface in which the (100) plane is connected in steps in the atomic layer order is obtained. In the process of exposing the tilted substrate to hydrogen plasma at a hydrogen pressure of 10 to 50 Torr and a microwave output of 200 to 1200 W, the substrate is exposed to a temperature of 700 to 1200 ° C for 0.5 to 5 hours. Including processing.

Further, the predetermined substrate temperature is between 700 ° C and 1100 ° C, preferably 830. C.

The volatile hydrocarbons constituting the source gas are alkanes or alkenes. The alkane is methane, hexane or propane, and the alkene is preferably ethylene or propylene.

The iodide compound constituting the source gas is preferably hydrogen sulfide or carbon disulfide, but may be an organic iodide compound, for example, a lower alkyl mercaptan.

In the method for producing an n-type semiconductor diamond according to the present invention, the microwave plasma is composed of a raw material gas of methane having a concentration of 0.1 to 5%, hydrogen sulfide having a concentration of 1 ppm to 2000 ppm, and hydrogen. The raw material gas is maintained at a pressure of 30 to 60 Torr while flowing at a flow rate of 200 ml · min ” ¹ and is excited at a microwave frequency of 2.45 GH and a microwave output of 300 to 400 W.

According to the method for manufacturing an n-type semiconductor diamond of the present invention by such a method, the carrier has n-type conductivity supplied from a single donor level, has high mobility, and has few crystal defects. Type semiconductor diamond can be manufactured.

In order to achieve the second object, the n-type semiconductor diamond manufactured by the manufacturing method of the present invention has an impurity atom as an i-atom, which forms a single donor level of 0.38 ev. are doing.

Further, the n-type semiconductor diamond has perfect crystallinity that is T ^3/2 dependent in a temperature range where the carrier mobility is equal to or higher than room temperature with respect to the temperature (T), and can be applied to semiconductor electronic devices.

Furthermore, this n-type semiconductor diamond has perfect crystallinity in which light emission by free excitons and bound excitons is observed, and can be applied to semiconductor electronic devices.

Furthermore, this n-type semiconductor diamond has a carrier concentration of at least 1.4 × 10 ^{: 3} cm— ³ at room temperature and a carrier mobility of 580 cm ² V— ¹ · s It has the perfect crystallinity described above and can be applied to semiconductor electronic devices.

Further, the n-type semiconductor diamond has perfect crystallinity in which the half width of the diamond peak in the Raman spectrum is 2.6 cm— ^; or less, and can be applied to semiconductor electronic devices.

Therefore, when the n-type semiconductor diamond of the present invention is used, a pn junction having excellent electrical characteristics can be formed by combining with the conventional p-type semiconductor diamond fabrication technology, and the semiconductor diamond thin film can be formed. This makes it possible to industrially manufacture semiconductor electronic devices, thereby realizing the manufacture of small high-power devices, high-output high-frequency devices, high-temperature operating devices, and the like. BRIEF DESCRIPTION OF THE FIGURES

The present invention will be better understood from the following detailed description and the accompanying drawings, which illustrate embodiments of the invention. The embodiments shown in the accompanying drawings do not specify the present invention, but are used only for facilitating explanation and understanding. In the figure corresponding to the first purpose,

FIG. 1 is a schematic diagram showing a substrate surface state by the substrate pretreatment of the present embodiment.

FIG. 2 is an atomic force microscope (AFM) photograph of the substrate surface shape obtained by the substrate pretreatment of this example.

FIG. 3 is an optical microscope photograph comparing the surface shapes of an i-doped n-type semiconductor diamond grown epitaxially on a substrate subjected to the substrate pretreatment and a substrate not subjected to the pretreatment according to the present embodiment.

FIG. 4 is a schematic configuration diagram of the microwave plasma CVD apparatus used in the present embodiment. FIG. 5 is a view showing the conditions for homoepitaxial growth of an i-doped n-type semiconductor diamond in this example.

For the second purpose,

FIG. 6 is a diagram showing the temperature dependence of the carrier concentration of the i-doped n-type semiconductor diamond of this example.

FIG. 7 is a diagram showing the temperature dependence of the mobility of the i-doped n-type semiconductor diamond of this example measured by the Hall coefficient. FIG. 8 is a diagram showing the temperature dependence of the mobility of a diode n-type semiconductor diamond grown at a substrate temperature of 780.degree.

FIG. 9 is a diagram showing a comparison of the mobility between the i-doped n-type semiconductor diamond of the present example and the conventional n-type n-type semiconductor diamond.

FIG. 10 is a diagram showing the Raman spectrum of the i-doped n-type semiconductor diamond of this example.

FIG. 11 is a diagram showing a spectrum of free exciton light emission and bound exciton light emission of the i-doped n-type semiconductor diamond of this example.

FIGS. 12A and 12B are diagrams showing the crystallinity of the i-doped n-type semiconductor diamond of this example. FIG. 12A shows a secondary electron microscope (SEM) image, and FIG. 12B shows a reflection electron diffraction (RHEED) pattern. ing.

FIG. 13 is a diagram showing the profile of the atomic concentration of secondary ion mass spectrometry (S IMS) in the i-doped n-type semiconductor diamond of this example. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the best embodiment of the method for producing an n-type semiconductor diamond of the present invention will be described in detail with reference to the drawings.

The n-type semiconductor diamond growth method may be a growth method using any of electricity, heat and light energy, depending on the method of activating the source gas. In this embodiment, however, only the electric energy and the heat energy are used. An epitaxial growth method using a microwave plasma CVD (chemical vapor deposition) system is used.

First, the pretreatment of the epitaxial growth substrate of the present embodiment will be described. This substrate pretreatment is performed in the (1) diamond (100) plane direction with the surface normal to the 100> direction or the 0100> direction or the 0100> direction. An inclined substrate is manufactured by mechanical polishing so that it is inclined at an angle (inclination angle) in the range of 1.5 to 6 degrees with respect to the 100> direction in the plane formed by The feature is that the substrate is exposed to hydrogen plasma to smooth the surface.

In the mechanical polishing of (1), diamond abrasive grains having a grain size of 0.5 μm or less are used.

The surface smoothing treatment of (2) uses a microwave plasma device described below. , 2.45 GHz microwave output 200 to 1200 W, hydrogen pressure 10 to 50 Torr, substrate temperature 700 to 1200 ° C, processing time 0.5 to 5 hours. This surface smoothing treatment can also be performed by exposing it to an oxidizing flame of a combustion flame such as acetylene.

Figure 1 (a) shows the substrate pretreatment described above, that is, the surface normal of the diamond (100) substrate is in the plane defined by the 100> direction, especially the 0 10> direction, or the 100> direction, especially the 001> direction. > This is a schematic cross-sectional view showing the state of the surface of an inclined substrate that has been mechanically polished so as to be inclined at any angle (inclination angle) in the range of 1.5 to 6 degrees based on the direction.

As shown in this figure, the surface of the inclined substrate has a predetermined inclination angle (h) set at the time of mechanical polishing of the envelope surface. However, when viewed microscopically, the surface of the inclined substrate has very many irregularities on the atomic order.

FIG. 1 (b) shows the above-mentioned substrate pretreatment, that is, the inclined substrate was exposed to the above-mentioned hydrogen plasma to perform a smoothing process, and the state of the surface after the smoothing process was shown in a schematic cross-sectional view. Things.

As shown in this figure, the surface of this substrate is smoothed in the atomic order by this smoothing process, and the (100) plane becomes a continuous surface in the order of the atomic layer in a step-like manner.

FIG. 2 (a) is an atomic force microscope (AFM) photograph of the surface of the inclined substrate prepared by the mechanical polishing described in (1) above.

From this figure, it can be seen that there are many steps on the surface and that there are many fine streaks due to the abrasive grains used for mechanical polishing.

That is, as shown in the schematic diagram of FIG. 1 (a), the surface of the inclined substrate produced by the above (1) has a predetermined inclination angle set at the time of mechanical polishing, as the envelope surface of the inclined substrate surface. , Microscopically, there are many irregularities on the atomic order.

FIG. 2 (b) is an AFM photograph of the surface of the inclined substrate after the above-mentioned smoothing treatment (2) is performed.

From this figure, it can be seen that the steps shown in Fig. 2 (a) are reduced, and fine streak marks due to abrasive grains are also eliminated, and the surface is smoothed at the atomic order. That is, as shown in the schematic diagram of FIG. 1 (b), the surface of this substrate is smoothed in the atomic order by the surface smoothing treatment of the above (2), and the (100) plane is an atomic layer. The surface becomes continuous in a step-like fashion.

Fig. 3 (a) shows a micro-process using the raw material gas obtained by diluting methane gas and hydrogen sulfide gas with hydrogen gas, as described in detail below, on the substrate that has been subjected to the above-mentioned substrate pretreatments (1) and (2). 1 is an optical microscope photograph of the surface of a 1-μm-thick n-type diamond thin film grown epitaxially by mouth-wave plasma CVD. Figure 3 (b) is an optical micrograph of the surface of an n-type diamond thin film epitaxially grown on the (100) substrate without the substrate pretreatment described in (1) and (2) above. Except for the above, it was prepared under the same conditions as above.

As can be seen from FIG. 3 (a), the surface of the n-type diamond thin film epitaxially grown on the substrate subjected to the above-mentioned substrate pretreatments (1) and (2) is very flat, and has an atomic order. It turns out that it is flat. In addition, as described in detail below, this n-type diamond thin film has a very high perfect crystal in measurement for evaluating crystallinity, for example, measurement of temperature dependence of mobility, exciton emission, or Raman spectrum. It shows the nature.

On the other hand, as can be seen in Fig. 3 (b), the surface of the n-type diamond thin film epitaxially grown on the substrate not subjected to the substrate pretreatment in (1) and (2) above has a triangular pyramidal twin It can be seen that the surface has grown and that the surface has severe irregularities reflecting polishing marks. In addition, this n-type diamond thin film has a high perfect crystallinity such as an n-type diamond thin film epitaxially grown on the substrate pretreated in (1) and (2) above in the measurement for evaluating the crystallinity. Is not shown.

The substrate surface parallel to the (100) plane, that is, mechanically polished at an inclination angle of 0 and subjected to the smoothing treatment in (2), has a (100) plane as shown in Fig. 1 (c). Fluctuated up and down in the order of the atomic layer, that is, the (100) plane became a series of irregularities, and the surface of the n-type diamond thin film epitaxially grown on this plane was as shown in Fig. 3 (b). Twinning occurs, and good results cannot be obtained in the above-described measurement for evaluating crystallinity.

As described above, as a pretreatment of the substrate for epitaxial growth, (1) <100> In the plane defined by the surface normal direction of the substrate (100) and the direction of the <100> direction, especially the <101> direction or the <100> direction, the <100> direction A tilted substrate is mechanically polished so that it is tilted at an angle (tilt angle) in the range of 1.5 to 6 degrees with respect to the direction. Then, (2) this tilted substrate is subjected to hydrogen plasma. By exposing and smoothing the surface, the surface is smoothed in the atomic order, and the surface in which the (100) plane is in the atomic layer order in a step-like form is obtained. By epitaxial growth, n-type diamond with good crystallinity can be epitaxially grown.

Next, the microwave plasma CVD apparatus used in the present embodiment will be described. FIG. 4 is a schematic configuration diagram of a microwave plasma CVD apparatus used in the present embodiment.

Referring to FIG. 4, a microwave plasma C VD apparatus 10 used in the present embodiment is composed of, for example, a microwave generator 1 of 2.45 GHz, an isolator and a power monitor 13, and a tuner 5. A reaction tube 7 to be irradiated with microwaves, a vacuum pump (not shown) for evacuating the reaction tube 7, and a gas supplied to the reaction tube 7 by switching between a mixed gas as a source gas or a purge gas. A supply line 9, a plurality of optical windows 11 and 11, a substrate holder 13 provided in the reaction tube, and a temperature for heating or cooling the substrate 15 placed on the substrate holder 13 A control system 17 is provided, and a gas is supplied onto the substrate 15 to generate microwave plasma 19. The substrate temperature is monitored with an optical pyrometer.

Next, conditions for epitaxial growth of n-type semiconductor diamond by microwave plasma CVD will be described. The growth conditions vary depending on the raw material, temperature, pressure, gas flow rate, impurity addition amount, substrate area and the like.

FIG. 5 is a diagram showing the growth conditions for the iodo-doped semiconductor diamond homoepitaxy in this example. Explaining with reference to FIG. 5, in this embodiment, the reaction gas uses a mixed gas of hydrogen / hydrogen sulfide / hydrogen as the raw material gas. Any gas mixture of compound gas and hydrogen can be used as a source gas. Hydrocarbons are used as a source of carbon, which is a constituent element of diamond, zeo-compound gas is used as a source of one atom of donor, and hydrogen is used as a carrier gas. For example, methane, ethane, and propane are used as alkanes, and ethylene and propylene are used as alkenes.Methane, as a volatile hydrocarbon, can easily minimize the carbon supply of diamond's constituent elements. Most preferred.

Examples of the thio compound include inorganic thio compounds such as hydrogen sulfide (H ₂ S) and carbon disulfide (CS ₂ ), and organic thio compounds such as lower alkyl mercaptan, with hydrogen sulfide being most preferred.

Therefore, it is preferable to use methane / hydrogen sulfide / hydrogen as the mixed gas. The methane concentration in the mixed gas is 0.1% to 5%, preferably 0.5% to 3.0%. The concentration of hydrogen sulfide in the gas mixture is 1 ppm to 2000 ppm, preferably 5 ρπ! Good to use at ~ 200 ppm.

In this embodiment, the methane concentration is 1%, and the hydrogen sulfide is 10 to 10 ppm. As the concentration of hydrogen sulfide increases, the carrier concentration increases. In this concentration range of hydrogen sulfide, the mobility is most preferably 5 Oppm because the maximum amount of hydrogen sulfide is 50 ppm.

The total gas flow rate depends on the scale of the apparatus, for example, the volume of the reaction tube, the supply gas flow rate, the exhaust volume, and the like. In the present embodiment, the total gas flow rate is 200 ml / min.

The gas flow rate is controlled by a mass flow controller corresponding to each gas type.The amount of hydrogen sulfide added is controlled by a mass flow controller using a mixed gas cylinder of, for example, 100 ppm hydrogen sulfide / hydrogen, diluted with carrier hydrogen. Thus, the ratio is controlled to a predetermined ratio.

In this embodiment, a mixed gas cylinder of 10 Oppm hydrogen sulfide / hydrogen is used. In this embodiment, the hydrogen sulfide concentration is set to 5 Oppm, so when the total flow rate is 20 Oml / min, the carrier hydrogen gas is set to 10 Oml / min, and the mixed gas cylinder of 10◦ppm hydrogen sulfide / hydrogen is used. By flowing 10 Oml / min, the hydrogen sulfide concentration can be set to 5 Oppm as a whole.

In the microwave plasma CVD, the pressure is approximately within a range of 30 to 60 T 0 rr, and in this embodiment, the pressure is set to 4 OTo rr. In microwave discharge, glow discharge is maintained at a relatively high pressure. 0/5534-Force at which the temperature of the substrate on which diamond is deposited is 700 ° C to 1100 ° C is 830 ° C in this embodiment.

In addition, although Ib diamond was used as the substrate diamond, it is not limited to this type of diamond, and may be la or II type. Further, in this embodiment, diamond is homoepitaxially grown on the (100) plane, but is not limited to the (100) plane, and may be, for example, the (111) plane or the (110) plane.

Next, the manufacturing process of the n-type semiconductor diamond in this embodiment will be described.

First, as a pre-treatment of the substrate for the epitaxial growth, the diamond (100) oriented substrate surface was polished using diamond abrasive grains with a grain size of 0.5 μm or less. A machine that tilts at an angle (tilt angle) in the range of 1.5 to 6 degrees with reference to the 100> direction in the plane defined by the direction 010> direction or the 100> direction, particularly the 001> direction. A polished tilted substrate was prepared, and this tilted substrate was exposed to hydrogen plasma at a microwave output of 2.45 GHz, 200 to 1200 W, and a hydrogen pressure of 10 to 50 Torr, using the microwave plasma apparatus described above. The surface is smoothed at a substrate temperature of 700 to 1200 ° C and a processing time of 0.5 to 5 hours. This surface smoothing treatment can also be performed by exposing it to an oxidizing flame of a combustion flame such as acetylene.

Next, the substrate is subjected to a cleaning process, and is set on the substrate holder, and hydrogen purge is repeated several times from the gas supply line to remove nitrogen and oxygen in the vacuum vessel. Next, while controlling the substrate holder, the substrate surface temperature is controlled to be 830 ° C. and the pressure is controlled to 40 Torr. The substrate surface temperature is measured by, for example, an optical pyrometer. Next, microwave discharge was performed under pressure control of 40 T 0 rr, and the hydrogen gas for purging was switched to a mixed gas of 1% methane / 50 ppm hydrogen sulfide diluted with hydrogen at the gas supply line, and 20 Oml was added to the reaction tube. When introduced at / min, plasma is generated above the substrate. This plasma flow is supplied to the diamond substrate, and the diamond thin film grows epitaxially.

When the film thickness reaches a predetermined value, switch the gas supply line to hydrogen purge, stop microwave discharge, and stop or cool the substrate. When the temperature finally returns to room temperature, remove the diamond substrate from the substrate holder of the reaction tube that has returned to normal pressure.

On the diamond crystal thin film thus manufactured, an electrode whose ohmic property was confirmed at a measurement temperature of 250 to 550 K was formed.

The diamond crystal thin films thus produced all show a negative Hall coefficient at the measurement temperature of 250-550 K, the mobility at room temperature is as high as 580 cm ² / V · s, and the reflection electron diffraction ( RHEED), a clear Kikuchi pattern can be observed, and the crystallinity of the crystal thin film is extremely high.

As is clear from the above description, according to the method for producing an n-type semiconductor diamond of this example, an n-type semiconductor diamond having high mobility and good crystallinity can be obtained.

Next, the characteristics of the n-type semiconductor diamond thus manufactured will be described in detail.

FIG. 6 is a diagram showing the temperature dependence of the carrier concentration of the n-type semiconductor diamond according to the present embodiment.

As can be seen from FIG. 6, the carrier concentration is increased to 10 ¹² ~10 ¹⁵ cm 3 as the temperature rises, the conductivity of the diamond film is ^{1. 3 x 10- 3 Ω ο πτ} 1 at room temperature. As can be seen from the figure, the carrier concentration shows a complete exponential dependence on the reciprocal of temperature, which indicates that carriers are supplied only from a single donor level. . As can be seen from Fig. 6, the activation energy of the donor level is 0.38 eV.

That is, the n-type semiconductor diamond of the present invention is an n-type semiconductor diamond in which zeo (S) atoms form a single donor level with an activation energy of 0.38 eV.

FIG. 7 is a diagram showing the temperature dependence of the mobility of the n-type semiconductor diamond according to the present embodiment measured by the Hall coefficient.

At measurement temperatures of 250 to 550 K, all exhibit a negative Hall coefficient.

As is clear from FIG. 7, the carrier concentration at room temperature is 1.4 xl 0 ¹³ cnT ³ and the mobility is 580 cm ² / V · s. FIG. 8 is a diagram showing the temperature dependence of the mobility of n-type semiconductor diamond grown at 780 ° C. measured by the Hall coefficient. The growth conditions other than the substrate temperature are the same, but since the substrate temperature is low, the amount of indium (S) incorporated into the crystal is small.

In the example shown in FIG. 8, the mobility is 980 cm ² / V · s, and therefore, the n-type semiconductor diamond of the present invention exhibits extremely high mobility even when the doping amount of iodine is small.

The electron mobility of type IIa diamond is estimated to be about 2000 cm ² V ¹ .s—. However, according to the manufacturing method of this example, since the crystallinity can be extremely high, the use of I la-type diamond substrate ^{^{^{1 0 3 cm 2 V 1 ·}}} s 1 single mobility is possible.

FIG. 9 is a graph showing a comparison of the mobility between the n-type semiconductor diamond doped with n-type (S) of the present embodiment and the n-type semiconductor diamond doped with phosphorus (P).

In FIG. 9, the mark indicates the completeness of the S-doped n-type semiconductor diamond according to the present invention at a growth temperature of 780 ° C. and the mark 8 at 830 ° C. The result is a conventional P-doped n-type semiconductor diamond.

In conventional P de one flop n-type semiconductor diamond is about mobility 1 0 cm ² / V • s at room temperature, is about 3 0 cm ² / V · s at most value (Diamond and Rela ted Materials 7 (1998) 540-544, see S. Koizumi et al).

On the other hand, the mobility of the S-doped n-type semiconductor diamond of this embodiment is about 600 cm ² / V · s or more, as described above, and is extremely high.

Furthermore, the Iou (S) doped n-type semiconductor diamond according to the production method of the present invention, contrary to the temperature dependence shown when the temperature characteristics of the mobility is large crystal defects decreases as a high temperature, T ^{3 kappa 2} Dependence is shown.

This temperature characteristic indicates that the carrier scattering process is dominated by the phonon, and is observed only in single crystals with high perfect crystallinity. Therefore, the ゥ -type (S) -doped η-type semiconductor diamond of this example has very few crystal defects, and therefore the carrier source is not a crystal defect or the like but a dopant atom, and is used as a semiconductor electronic device. It can be seen that it has perfect crystallinity. FIG. 10 is a diagram showing the Raman spectrum of the n-type semiconductor diamond of this example. As is clear from Fig. 10, there is no peak other than the peak at the wave number of 1333 cm- ¹ and its half width is extremely narrow at about 2.6 cm. Therefore, the n-type semiconductor diamond of this example has extremely high crystallinity. Although not shown, the wave number of an n-type semiconductor diamond epitaxially grown without performing the above-mentioned substrate pretreatment is about 6 cm- ¹ .

FIG. 11 is a diagram showing the spectra of free exciton emission and bound exciton emission of the n-type semiconductor diamond of this example. As is evident from FIG. 11, free exciton emission (FE) around 235 nm and bound exciton emission (BE) around 238 nm are observed in the n-type semiconductor diamond of this example. This indicates that the doped hole is present at the lattice point of the diamond lattice and forms a complete donor level in the band gap of the diamond crystal. In addition, free exciton light emission and bound exciton light emission are not observed in n-type semiconductor diamond grown epitaxially without performing the above-mentioned substrate pretreatment.

Figure 12 (a) shows a secondary electron microscope (SEM) photograph, and (b) shows a backscattered electron diffraction (RHEED) pattern. As is clear from FIG. 12 (a), the surface of the n-type semiconductor diamond of this example is very smooth. Then, as is clear from FIG. 12 (b), a very clear Kikuchi pattern is generated, and it can be confirmed that the crystallinity is extremely high.

FIG. 13 is a diagram showing the profile of the atomic concentration of the n-type semiconductor diamond of this example measured by secondary ion mass spectrometry (S IMS). From FIG. 13, it can be seen that in the n-type semiconductor diamond of the present example, ゥ (S) is doped at a constant concentration, and this ゥ (S) is at least 10 ¹³ cm− ³ or more, which is the detection limit of SIMS. You can see that it has been done.

As is clear from the above description, the n-type semiconductor diamond fabricated in this example has n-type conductivity in which carriers are supplied from a single donor level, has few crystal defects, and has low mobility. Is big. Therefore, a pn junction with excellent characteristics can be formed by combining it with the conventional p-type semiconductor diamond fabrication technology. Note that the present embodiment describes an exemplary embodiment of the present invention, and various changes, omissions, and additions can be made in the embodiment without departing from the spirit and scope of the present invention. . Therefore, the present invention is not limited to the embodiments, but should be understood to cover the scope defined by the elements recited in the claims and the equivalents thereof. Industrial applicability

As described above, the n-type semiconductor diamond and the method for manufacturing the same according to the present invention enable industrial manufacture of semiconductor electronic devices using a semiconductor diamond thin film, such as small high-power devices, high-power high-frequency devices, and high-temperature operating devices. Manufacturing can be realized.

Claims

The scope of the claims

1. In a method for producing an n-type semiconductor diamond, a diamond substrate is formed into an inclined substrate by mechanical polishing, the surface of the inclined substrate is smoothed, and a raw material gas comprising volatile hydrocarbons, thio compounds, and hydrogen gas is microwaved. A method for producing an n-type semiconductor diamond, characterized in that an n-type semiconductor diamond is epitaxially grown on the smoothed substrate while being excited by plasma and maintaining a predetermined substrate temperature.

2. The method for producing an n-type semiconductor diamond according to claim 1, wherein the diamond substrate is a diamond (100) plane oriented substrate.

3. The tilted substrate has a diamond (100) plane oriented in a plane defined by the plane normal to the plane of the substrate and the <100> direction of the substrate. 2. The method for producing an n-type semiconductor diamond according to claim 1, wherein the inclined substrate is mechanically polished so as to be inclined at any angle in a range of 1.5 to 6 degrees with respect to the direction.

4. The method for producing an n-type semiconductor diamond according to claim 1, wherein the smoothing process is a process of exposing the inclined substrate to hydrogen plasma or a process of exposing the substrate to an oxidizing flame of a combustion flame such as acetylene.

5. The process of exposing the inclined substrate to the hydrogen plasma is performed in a plasma having a hydrogen pressure of 10 to 50 T 0 rr and a microwave output of 200 to 1200 W at a substrate temperature of 700 to 1200 ° C and a processing time of 0.5 to 5 3. The method for producing an n-type semiconductor diamond according to claim 1, wherein the method is exposure treatment for a time.

6. The method for manufacturing an n-type semiconductor diamond according to claim 1, wherein the predetermined substrate temperature is 700 ° C to 110 ° C, preferably 830 ° C.

7. The method for producing an n-type semiconductor diamond according to claim 1, wherein the volatile hydrocarbon is an alkane or an alkene.

8. The method for producing an n-type semiconductor diamond according to claim 7, wherein the alkane is methane, ethylene, or propane.

9. The method for producing an n-type semiconductor diamond according to claim 7, wherein the alkene is ethylene or propylene.

10. The method for producing an n-type semiconductor diamond according to claim 1, wherein the iodide compound is hydrogen sulfide or carbon disulfide.

11. The method for producing an n-type semiconductor diamond according to claim 1, wherein the iodide compound is an organic iodide compound.

12. The method for producing an n-type semiconductor diamond according to claim 11, wherein the organic compound is a lower alkyl mercapone.

13. The microwave plasma while flowing concentration 0.1% to 5% of methane, the feed gas comprising hydrogen sulfide and hydrogen concentration LPPM to 2000 ppm at a flow rate 200m ¹ · mi n 1 30~60 T maintaining a pressure of orr, characterized in that it excited by microwave frequency 2. 45 GH _Z and microwave output 3◦ 0~400W, manufacturing method of the n-type semiconductor diamond according to claim 1, wherein.

14. An η-type semiconductor diamond produced by the method for producing an η-type semiconductor diamond according to any one of claims 1 to 13.

15. The n-type semiconductor diamond according to claim 14, wherein the impurity atoms are zeo atoms, and the zeo atoms form a donor level of 0.38 ev. Mondo.

16. The n-type semiconductor diamond according to claim 14, wherein the temperature (T) dependency of carrier mobility is T 3 ′ ^{/ 2} in a temperature range of room temperature or higher.

17. The n-type semiconductor diamond according to claim 14, wherein light emission by free excitons and bound excitons is observed.

18. At room temperature, it is the carrier concentration is 1. 4 X 10 ¹³ cm- ³ or more, and the carrier mobility of 580 cm ² ^V-; and characterized in that · s ¹ or more, according to claim 14 N-type semiconductor diamond.

19. The n-type semiconductor diamond according to claim 14, wherein the half width of the diamond peak in the Raman spectrum is 2.6 cm- ¹ or less.

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